I. Field of the Invention
The present invention relates generally to propellant charge systems for large caliber artillery pieces, more particularly, to modular artillery charge systems or MACS, and involves improvements in a load, assembly and packaging process for manufacturing field modular charge units for singular and multi-unit propellant charge systems. Specifically, the invention is directed to an improved alignment fixture which fixes the relative positions of the case and core tube during the time the case is filled and further facilitates the lid to be guided into place and inserted with precision.
II. Related Art
Propellant charges for cannon artillery systems, primarily large caliber weapons systems such as 155 mm howitzers, etc., typically include plurality of coordinating modular charge units serially loaded behind the shell. The individual modular charge units are generally cylindrical in shape, frequently having a length to diameter ratio approaching 1. A central axial opening is provided through each unit to facilitate ignition of that and consecutive units. Such a system concept is illustrated, for example, by Reinelt, et al., in U.S. Pat. No. 4,702,167.
Particular embodiments of such modular units are of a three-piece design, which includes a combustible case body, normally of nitrocellulose, having a closed end and an open end, a combustible cap or lid adapted to fit or nest in and seal into the open end of the case body, and a perforated combustible central or core tube which fits over raised rims in the central bores of and connects the central openings provided in the closed ends of both the relatively rigid case body and lid to form a continuous central bore for containing core igniter bags. Top and bottom recesses are provided to accommodate two end igniter bags. This assures proper ignition of a number of serially placed modular charges. Up to eight modular charges may be employed in firing a 155 mm howitzer, for example.
The MACS load, assemble and pack process utilizes a series of discreet workstations, each of which is designed to accomplish a specific operation on the case, charge and additive materials. The present invention deals primarily with the provision of a significantly better approach to one difficult manual portion of the process including an operation at a loading station in which the case and core tube must be held in precise alignment during filling and during the operation in which the lid or cap is guided and inserted into place to seal the modular unit.
In the past, the operation has presented problems. No positive positioning devices existed and the central tube or core was placed over the rim or lip extension of the opening formed in the bottom of the case by hand and held in place while a weighed amount of propellant was poured about the tube to fill the case. Proper alignment was thus dependent on the repetitive skill of the operator. This had to be done while the assembly was vibrated to achieve proper propellant density. After the case was filled, the lip of a central opening in the cap or lid had to be fit over the central tube and the edge nested inside the case sidewall. Of course, if the central tube was not axially aligned so as to be concentric with the lid or cap and case, when the lid was fitted to the filled case and installed into the top of the case and over the top of the core tube, the core tube and lid could be easily damaged resulting in rejection of the module. This occurred often enough to be considered a severe defect in the process, one for which there was a definite need for a solution.
Accordingly, it is a primary object of the present invention to provide a system that automatically provides and maintains proper alignment among the case body core tube and lid during filling and capping assembly of a MACS charge.
It is a further object of the present invention to provide alignment an fixture that is capable of maintaining alignment of top and bottom protrusions utilized in lid/case body assembly in certain MACS charges, such as the XM 231 and XM 232 howitzer charges.
A further object of the present invention is to provide an alignment fixture that holds the case and lid in the specific orientation and utilizes a locking and expanding mandrill to center the core tube in position.
A yet still further object of the present invention is to provide an alignment fixture which holds the case and lid in a specific orientation utilizing a locking and expanding mandrill to center the core tube wherein the mandrill further acts as a guide for the lid as it is being inserted.
Another object of the present invention is to provide an alignment fixture which includes a holding fixture for the lid equipped with a device that inserts the lid in the case body to a controlled depth.
Still another object of the present invention is to provide an alignment fixture and system in which, once the case is loaded with propellant, the fixture is closed and the lid insertion is performed automatically.
An additional object of the present invention is to provide a mechanized processing station that includes an alignment fixture and lid insertion device that prevents core tube and/or lid damage during filling and capping assembly of modular units.
Additional objects and advantages regarding the fixture system of the invention will become apparent to those skilled in the art upon familiarization with the specification, drawings and claims associated with this specification.
The present invention provides solutions to several severe problems encountered in production of modular artillery charge system propellant units and specifically problems stemming from an inability to maintain proper alignment of the parts during manual loading and capping operations by the provision of a mechanized system including an alignment fixture which simplifies and improves the alignment of the case body and center case tube during loading and guides the lid into place during the lid insertion operation or capping step.
The alignment fixture is an assembly including a metal base member which may be machined aluminum base having a bottom and sidewall adapted to receive the lower portion (bottom and partial sidewall) of the modular unit case body of the MACS charge. The fixture base includes a central bore for receiving an elongated centering rod or spindle directed up through the center of the case body and carries a flexible peripheral member or expander which is expanded by a similarly shaped cam lock member which fits over the upper centering rod to positively position the upper portion of the center core tube or ignition tube. The cam lock portion of the mandrill is tapered at the upper end and also acts as a guide for the lid as it is being inserted. The cam lock member or mandrill operates vertically to lock and unlock the module core tube. The holding fixture for the lid is equipped with a fluid operated, preferably, an air cylinder of adjustable stroke that inserts the lid in the case body after the fixture is closed. The stroke depth of the cylinder is controlled with cam operated limit valves that may be adjusted to insert the lid to a specific depth in the case body. This device further aligns cap protrusions with case recesses in accordance with the desired orientation for insertion of the lid.
In operation, after the operator has placed the case body in the alignment fixture, the core tube is inserted over the raised cam lock member or mandrill and the lower end of the core tube is properly seated over the lower extension in the case body. The mandrill is lowered to expand the flexible peripheral member to fix the orientation of the upper portion of the core tube with respect to the alignment fixture. The alignment fixture is attached to a vibration table which is initiated while the operator loads the case with a pre-weighed amount of propellant thereby assuring proper propellant fill. After the propellant is loaded, the pivot plate is rotated to a latched position above and parallel to the base plate.
After that, the lid insertion is performed automatically by activation of the air cylinder and the vibration table is shut off at the end of the cycle.